1. Field of the Invention
The invention relates to a device for measuring the mass rate of flow which works according to the coriolis principle and has two measurement tubes and a vibration converter.
2. Description of Related Art
Coriolis devices for measuring the mass rate of flow with two or more measurement tubes typically have two measurement tubes which run parallel to one another at least in sections, between which there are at least one vibration exciter and at least one vibration sensor as the vibration converter. In this connection, the two measurement tubes can be caused to vibrate differently from one another, the mass of a medium flowing through the measurement tubes typically being determined via phase shifting of the achieved vibrations of the measurement tubes relative to the excitation vibration and between two points on the measurement tubes spaced apart from one another.
In the coriolis mass flow rate measuring device, if there are exactly two straight measurement tubes which run parallel, generally vibration excitation of the two measurement tubes in phase opposition in their common plane, at one resonant frequency is selected. Compared to coriolis measurement devices with only a single measurement tube, it is advantageous that, due to vibrations, the center of gravity of the vibrating system does not change. Viewed from the outside, the coriolis mass flow rate measuring device with two straight measurement tubes running parallel therefore behaves in a manner neutral to vibration, so that no faults due to natural vibration need be feared, since only the two measurement tubes vibrate, while the housing provided for the coriolis mass flow rate measuring device remains at rest. In this way, high zero point stability can be achieved.
The problem in the coriolis mass flow rate measurement devices known from the prior art with at least two measurement tubes is, among others, that they are complex and expensive to produce. In general, specifically, each device is made individually by hand to meet the required low tolerances and in order to be able to mount the individual devices of the coriolis mass flow rate measurement device, such as the vibration exciter and vibration sensor, correctly at all.